Bacteriostatic paper containing a guanidine salt and method of making the same



United States Patent 3,264,172 BACTERIOSTATIC PAPER CONTAINING A GUAN- SALT AND METHOD OF MAKING THE Carl W. Regutti, Glenshaw, Pa., assignor to Calgon Corporation, a corporation of Pennsylvania No Drawing. Filed May 8, 1964, Ser. No. 366,186 14 Claims. (Cl. 162-461) This application is a continuation-in-part of my copending application Serial No. 280,117, filed May 13, 1963, now abandoned.

This invention relates to manufacturing bacteriostatic paper. In particular, it relates to tissue paper having incorporated therein a small amount of a salt of guanidine or substituted guanidine as a microorganism inhibitor.

Prior to the present invention, no commercially successful tissue paper for inhibiting microorganisms was known. Absorbtive bacteriostatic tissue paper is desirable for the prevention of the spread of disease bacteria and other undesirable microorganisms and to inhibit the growth not only of pathogens but of bacteria which produce objectionable odors, stains, and the like. Such papers are particularly suitable for the manufacture of dental, hospital and professional towels, gowns, Wipes, baby diapers and the like.

Tissue paper generally lacks the strength and coherence to permit it to be dipped, sprayed, or otherwise effectively treated with a solution after it is formed and/or dried. Moreover, even if nondestructive spray techniques or other methods of surface application of chemicals to dry formed tissue paper were developed, the problem ofsatisfactory adherence of the chemical to the paper and heat stability would still remain. Such methods of application are not likely to provide uniform distribution of chemical throughout the thickness of the paper since it is applied mainly to the surface.

On the other hand, conventional bacteriostatic agents have not been successfully applied in the various wet stages of paper manufacture, primarily because such agents are likely to be almost entirely lost from the fibers during the agitation steps and from the wet or newly formed sheet in the various draining and pressing steps preliminary to drying. Many conventional bactericides are unsuitable for application in paper making systems because of properties such as excessive foaming, staining and odor. Tissue paper, paper diapers, toilet paper, sanit ary napkins, and the like must not contain toxic or irritating materials, and many conventional bactericides are unsuitable because of their toxicity to humans. My invention is useful for all of the above applications, as well as many others which will be obvious to men skilled in the art.

My method contemplates the use of a microorganism inhibiting agent exhibiting substantivity to the fibers of tissue paper so that it may be introduced to the pulp slurry or stock solution prior to the formation of the sheet or sprayed onto the pulp during formation of the sheet, and will remain a more or less permanent part of the fiber structure evenly distributed throughout. My invention preferably comprises adding a small amount of a salt of guanidine or an alkyl substituted guanidine salt in which the alkyl chain contains 12 to 14 carbon atoms to the stock suspension prior to formation into a sheet. Substituted and unsubstituted guanidine salts as hereinafter described may be referred to hereinafter simply as guanidine salts. They include salts such as the sulfate, carbon-ate, phosphate, 'oxalate, malate, and chloride. The chloride salt is often referred to as the hydrochloride, and the salts generally as acid salts. A guanidine chloride and a guanidine hydrochloride are different names for the same thing.

Generally, the guanidine salt is preferably added at the beginning of the paper making process, as, for example, to a Hi-Low pulper although it may be added at any time prior to conversion, for example, it may follow the bleaching step and precede the pickup by the Fourdrinier screen or other sheet-forming apparatus. The basic guanidine structure is not adversely affected by bleaching, however. The stock suspension which has been substantially prepared for formation into a sheet, I shall refer to as the prepared tissue paper stock suspension. It may be washed, lapped and dried, diluted, agitated, beaten bleached, transported, and/or otherwise treated after the addition of guanidine salt; the suspended fibers themselves, however should be substantially ready to be formed into a sheet prior to the addition. Any chemical treatment which does not substantially afiect the chemistry of the fibers may be employed after addition of the guanidine salt. The prepared stock suspension may be formed from a dried pulp of the type available in commerce for use by paper mills which are not associated with pulp mills. The dried pulp may be already treated with the guanidine derivative; i.e., the guanidine derivative may be added to the stock suspension in the pulp mill after the fibers are otherwise prepared for formation into a sheet although they are subsequently-dried for shipment to a paper mill. A prepared tissue paper stock suspension is a suspension of fibers which has already passed through the digester and blow tank steps, if such steps are employed, and is substantially capable of being formed into a sheet, although it maybe dried first instead. It may or may not be bleached. The optimum point of addition will vary depending on the heating process, holding time, alum, bleach, or other chemical treatment, pulp consistency, temperature, mixing time, and other variables before or after addition of guanidine salt. Generally, however, the preferred method of adding is to the pulper water before charging with pulp. This provides a dilute solution into which the pulp is charged and appears to give the most efficient use of the guanidine salt.

Among the alkyl guanidine salts which are useful in my invention are those in which the alkyl group contains about 12 to 14 carbon atoms. Some slight effects may be found by using alkyl guanidine salts in which the alkyl group contains about 10 or about 18 carbon atoms but these effects generally are much less significant than with 12 to 14 carbon atoms. Specific examples are tetradecyl guanidine acetate, dodecyl guanidine hydrochloride, hexadecyl guanidine sulfate, octadecyl guanidine phosphate and decyl guanidine lactate. The compound may be added to the prepared stock solution in the form of an aqueous or other solution or suspension or in the anhydrous state. Dodecyl guanidine hydrochloride is one of the more Water-soluble and also one of the more effective compounds and is preferred in my invention. The compound should be added to the stock suspension far enough in advance of the Fourdrinier screen or other sheet forming device, depending on the method of addition and other system variables, to insure even and complete distribution. The presence of soluble chlorides or of the chloride ion appears to improve the effectiveness of alkyl guanidine salts. The chlorine ion can help keep dodecyl guanidine hydrochlorid dispersed in systems containing high sulfate, silicate, acetate, phosphate, and other such ions (which tend to decrease the solubility or dispersibility of DGH and make it less effective in certain applications). The following example illustrates my invention:

EXAMPLE I Four batches of pulp were made and treated as follows. Two thousand pounds of dry digested and bleached pulp were added to 4,000 gallons of water to make a slurry containing about 6% pulp by weight in a hydropulper.

To this, pounds of wet-strength resin and a small amount of alum were added to make a prepared tissue paper stock solution, and 12 pounds of a 25% aqueous solution of dodecyl guanidine hydrochlorie (DGH) were added to the hydropulper. The slurry was then diluted to about 0.1% pulp consistency and then formed into a sheet on a Fourdrinier screen. It was dried on a Yankee drier at about 180 F.-212 F. for about five seconds. A control batch was made identical to the treated tissue with the exception that DGH was not added.

After the tissue was completely dried, sample discs were taken and placed on bacterial media inoculated with staphylococcus aureus to perform the zone of inhibition test described in Federal Specification UUP-510, Paper Sheeting, Bacteriostatic 4.4.2. The eight samples of 4-ply tissue paper (two from each DGH-treated batch) each exhibited approximately /2 mm. inhibition zones. No growth occurred under the discs. The control exhibited no inhibition zone and considerable bacterial growth was observed beneath the disc. Tests for DGH in the paper were made following the general method of Kjeldahl for nitrogen. Based on this test, the paper contained an average of 219 p.p.m. of DGH.

The same tissue paper was subjected to the self-sanitizing test #100196IT of th American Association of H Textile Chemists and Colorists entitled Anti-bacterial Finishes on Fabrics. Self-sanitizing is defined as the ability of material not only to inhibit bacterial growth, but also to reduce the number of bacteria present on the material by killing them. After two hours, the DGH- treated tissue paper had 53.6% fewer bacteria (of an original inoculum of Staphylococcus aureus ATCC #6538) than the untreated control, and after 6 /2 hours the DGH-treated tissue exhibited 98.9% fewer bacteria than the control.

EXAMPLE II Into a 150 H.P. Jones Hi-Low pulper, operating at 880 rpm. 3,400 gallons of clarified white water were added. Seven pounds of Biochek 60 DGH), as delivered were added and mixed thoroughly for one minute. Next, 2,000 pounds of dry lapp pulp (70% bleached kraft and sulfite) were charged into the pulper. This mixture was violently agitated for 7 minutes. Then the pulp slurry was dropped into a holding chest (non-operating refining chest). Another 3,400 gallons of water (pulper capacity) was added to the pulper. This water was used to flush the pulper and then added to the original charge into the holding chest. The pulp consistency in the holding chest was approximately 3.5%.

Next 0.5% based upon the fiber weight of a neutral curing type wet-strength resin (Kymene 557) and a direct type dye were added to the holding chest. After a period of mixing, the slurry was passed through a machine Jordan. By means of a consistency regulator, the furnish was brought to a consistency of approximately 0.1%..

Prior to the Jordan the pulp slurry had a Canadian Standard freeness of 700 cc. at 20 C. After the Jordan, the freeness was 500 cc. at 20 C.

The 0.1% slurry passed into a pressurized Beloit head box and onto a conventional Fourdrinier wire (speed 1,500 f.p.m.). The web was carried by a pick-up felt and directly transferred to face of a 10 ft. diameter Yankee drier. Then the dry tissu was pressed into a 4-ply product through a non-heated calender.

Bacteriostatic tissue made in this fashion passed Federal Specification UU-P-S 10: Bacteriostatic Paper Sheeting. In addition to making the paper effectively anti4bacterial, the extra benefit of making the paper softer also resulted from DGH application.

EXAMPLE III Table I TESTING THE BACTERIOSTATIC PROPERTIES OF PAPER PULP MATS TREATED WITH VARIOUS GUANIDINE SALTS Alkyl Guanidine Derivative Stock Water Inhibition Zones (mm) n-Octyl (Cs) guanidine hydrochloride A Distilled n-Octyl (C guanidine acetate A do Do n-Octyl (C guanidine glycolate n-O ctyl (Cs) guanidine lactate. n-Decyl (C10) uanidine hydrochlo de n-Deeyl (C10) guanidine acetates. n-Deeyl (Cm) guanidine glycol-ate.

n-Dodeeyl (C12) guanidine hydrochloride n-D )decyl (C12) guanidine acetate Do n-Dodeeyl (C12) guanidine malate n-D0deeyl (C1 guanidine nitrate n-Dodecyl (C guanidine phthalateu 11-13%180371 (C12) guanidine sulfate- Do n-Dorlecyl (C12) gua e carbo n-Tetradecyl (C14) guanid' e hydrochloride-.. n-Tetradecyl (O14) guanidine acetate n-Tetradeeyl (C14) guanidine glycolate n-Tetradeeyl (C14) guanidine lactate n-IIexadeeyl (O15) guanidine hydroehloride 0 n-Hexadecyl (Cut) guanidine acetate do Distil1ed Tap n-Hexadecyl (Cm) guanidine cyelamate nJIcxadecyl (Cw) guanidine lactate n-I-Icxadecyl (G 6) guanidine sulfate C n-otigadecyl (01s) uanidine hydrochloride 0 n-Octadeeyl (01a) guanidine acetaten-Octadecyl (C18) guanidine borate n-Octadecyl (C1 guanidine cyclarna n-Oetadecyl (Cm) guanidine glycolate" n-Octadeeyl (C guanidine laetate n-Oetadecyl (C1 guanidine phosphate n-Oetadecyl (O13) guanidine sulfate 1 A sulfide/% sulfate blend. 2 B 40% white/60% sulfate blend+kyrnene 557.

3 C 40% sulfite/60% sulfate blend+kymene 557+optieal brightner.

Kymene 557 and an optical brightener was added to some portions. Solidified tryptone glucose extract agar (TGE) plates were overlaid with a thin cell suspension of Micrococcus aureus, FDA 209. Discs were cut from each hand sheet and placed on this inoculated agar. These plates were refrigerated at 5 C. for 18 hours and then incubated for 24 hours at 34.5 C. After incubation, the discs were examined for zones of inhibition.

EXAMPLE IV Into a hydropulper was added white water, followed by ten pounds of Biochek 60 (25% DGH) and mixed thoroughly for several minutes. Next 1500 pounds of dry virgin pulp (sulfates and sulfites) and 300 pounds of broke were charged into the hydropulper, giving a pulp consistency of about 4.5%. This mixture was agitated, with recirculation, as violently as possible for 30 minutes. Then pitch dispersants, fluorescent dyes, and re-wetting agents were added and mixed. This pulp slurry was dropped into a refining chest, recycled for 25 minutes, and 150 pounds of fibrous filler was added. Next, alum was added and this slurry dropped into the machine chest. From there the pulp slurry passed into a consistency regulator, was diluted with white water, and proceeded into a disc refiner head box into which also was added wet-strength resin. After passing through the disc refiner, this dilute slurry entered the machine head box, into which was added antifoaming agents, and then onto a Fourdrinier wire. The Web was dried on a Yankee drier at an 18% crepe. Not only did the finished tissue paper product exhibit significant anti-bacterial properties by Zone of inhibition" test methods, but the undesirable musty odor normally characteristic of this paper had been significantly diminished 'by the DGH treatment.

Other tests using bacteria responsible for causing diaper rash through degradation of urine to ammonia revealed that paper made with alkyl guanidine hydrochlorides of C C C and C alkyl chain lengths could etfective- 1y inhibit growth and subsequent urine degradation by such organisms.

Laboratory tests have shown that the effectiveness (based on fungistatic bacteriostatic or bactericidal properties) of the treatment is generally related to the amount of DGH in the paper and that the amount of DGH in the paper is generally proportional to the amount added to the stock suspension, all other factors being equal. A small amount of DGH appears to be effective to some degree although the effectiveness of vary small amounts varies somewhat with the test procedure. So far as I am aware, there is no minimum amount below which DGH is totally without a bacteriostatic effect, nor is there an upper limit of concentration which is completely ineffective. The preferred practice, however, is to maintain a level of about 0.0015% to about .10% of guanidine salt in the pulper water at the time the pulp is added or alternatively about 0.05% to about 3% on the dry weight of pulp added. A preferred amount on the finished tissue is about 0.05 by weight in the case of dodecyl guanidine hydrochloride.

My invention is not limited to the above description and specific examples. It may be otherwise practiced within the scope of the following claims.

I claim:

1. In a method of making bacteriostatic tissue paper the step of forming a tissue paper stock suspension having therein an effective amount to about 3% of dodecyl guanidine hydrochloride on the dry weight of the stock and thereafter forming a paper sheet from said stock.

2. Method as claimed in claim 1 wherein the dodecyl guanidine hydrochloride is added to the water forming the vehicle for the suspension prior to the addition of pulp to form the paper stock suspension.

3. In a method of making bacteriostatic tissue paper the step of forming a tissue paper stock suspension having therein an effective amount to about 3% of a guanidine salt on the dry weight of the stock and thereafter forming a paper sheet from said stock.

4. Method of claim 3 in which the guanidine salt is an alkyl guanidine salt in which the alkyl group contains from about 12 to about 14 carbon atoms.

5. In a method of making tissue paper including the step of forming a sheet from a prepared tissue paper stock suspension, the improvement for imparting bacteriostatic properties to the tissue paper comprising the steps of forming a prepared tissue paper stock suspension containing an effective amount to about 3% of an alkyl guanidine hydrochloride on the dry weight of the stock.

6. Method of making bacteriostatic tissue paper comprising the steps of forming a prepared tissue paper stock suspension containing an effective amount to about 3% of a guanidine salt on the dry weight of the stock, forming the stock into a sheet, and drying said sheet.

7. Tissue paper containing an effective amount to inhibit bacterial growth to about 3% of guanidine hydrochloride.

8. Tissue paper containing an eifective amount to inhibit bacterial growth to about 3% of a guanidine salt.

9. In a method of making bacteriostatic paper, the steps of dissolving a salt of an alkyl guanidine in which the alkyl group contains 10 to 18 carbon atoms in water, adding a paper stock suspension to said. alkyl guanidine solution While agitating to form a suspension containing an eifective amount to about 3% of said alkyl guanidine on the dry weight of the stock, forming the resulting suspension into a paper sheet and drying.

10. A method as claimed in claim 9 wherein the alkyl guanidine is dodecyl guanidine hydrochloride.

11. A method as claimed in claim 9 wherein the alkyl group contains 12 to 14 carbon atoms.

12. A method as claimed in claim 9 wherein a source of chlorine atoms is added to the dissolving water.

13. A method as claimed in claim 9 wherein the alkyl guanidine is added in an amount equal to about 0.1% to about 1% on the weight of the pulp.

14. In a method of making baoteriostatic paper, the steps of dissolving a salt of an alkyl guanidine in which the alkyl group contains 10 to 18 carbon atoms in water, adding a paper stock suspension to said alkyl guanidine solution while agitating to form a suspension containing an eifective amount to about 3% of said alkyl guanidine on the dry Weight of the stock, forming the resulting suspension into a paper mat and drying.

References Cited by the Examiner UNITED STATES PATENTS 2,336,605 12/ 1943 Ernsberger et al 167-22 2,906,595 9/1959 Pelcak et al. 167-22 3,060,079 10/1962 Pattilloch 162161 FOREIGN PATENTS 471,873 3/1951 Canada.

DONALL H. SYLVESTER, Primary Examiner.

S. L. BASHORE, Assistant Examiner. 

3. IN A METHOD OF MAKING BACTERIOSTATIC TISSUE PAPER THE STEP OF FORMING A TISSUE PAPER STOCK SUSPENSION HAVING THEREIN AN EFFECTIVE AMOUNT TO ABOUT 3% OF A GUANIDINE SALT ON THE DRY WEIGHT OF THE STOCK AND THEREAFTER FORMING A PAPER SHEET FROM SAID STOCK. 